Whenever you add a domain name as hosted in some account, you usually set a pair of Name Servers to point it to that particular provider. On their end, 3 records are set up automatically right after the domain address is added - one A record and two MX records. The former is a numeric address, or IP address, which “tells” the domain name where its website is, while the other two are alphanumeric and they show the server that handles the emails for that particular domain address. The website and the e-mail hosting are usually considered to be one thing, when they're actually two different services. Having independent records for them will enable you to have them with different companies if you wish. As an illustration, some new company can have excellent uptime for your site, but you may not want to switch your e-mail messages from your current host and by using an A record to point the Internet domain to the former and MX records to have the e-mails with the latter, you will get the best of both providers. These records are checked when you wish to open a site or send an email - either way, the company whose name servers are used for the domain name is going to be contacted to retrieve the A and MX records and if you have set records different from their own, the right web/mail server will then be contacted and you are going to see the needed website or your email is going to be delivered.